It's a tiny little grey thing, separate to the circuit board. You might find it in the plastic rectangle at the top of the other half of the fob. Memory doesn't help me at the moment cos I did it a while ago.
If you really can't find it I'll split my other(spare) key and find it for you. But in the original key, there are only two things you can remove and you need both of them,
unless you want to keep and use the original, cut, key to turn the igniton, then leave the transducer in that and put the circuit board in your new fob. But you WILL find that the immobiliser will come back on if you leave too long between getting in the car after opening the door and starting the car.
If you really can't find it I'll split my other(spare) key and find it for you. But in the original key, there are only two things you can remove and you need both of them,
unless you want to keep and use the original, cut, key to turn the igniton, then leave the transducer in that and put the circuit board in your new fob. But you WILL find that the immobiliser will come back on if you leave too long between getting in the car after opening the door and starting the car.